The present invention relates generally to electronic energy meters, and more particularly to highly functional programmable electronic energy meters with systems for service identification and power quality analysis.
Programmable electronic energy meters are rapidly replacing electromechanical meters due to the enhanced functionality achieved using programmable logic integrated into solid-state electronic meters. Some of these meters can be used to meter various different electrical services without hardware modification. For example, meters having a voltage operating range between 98 Vrms to 526 Vrms are capable of operation with either 120 V or 480 V services. U.S. Pat. No. 5,457,621, dated Oct. 10, 1995, entitled SWITCHING POWER SUPPLY HAVING VOLTAGE BLOCKING CLAMP, assigned to ABB Power TandD Company discloses examples of such meters. In addition, some meters are constructed for use with any 3-wire or any 4-wire service, also disclosed in U.S. Pat. No. 5,457,621. Unless meters having this versatility are used, utilities must be careful to install the correct meter in relation to both configuration and electrical service supplied at the installation site. Unfortunately, meter installers are not always trained to detect or note service particularities which might indicate that the meter to be installed is not configured properly for a particular installation.
For this reason, some utilities configure the meters themselves to ensure better control over which meters are installed at which installation sites. However, such configuration activity adds to the installation cost and does not always reduce the risk that a meter configured for one service might inadvertently be installed at a site supplied by a different service. Therefore, there remains a need for an electronic meter which automatically detects the service type and voltage to which the meter is installed and which either automatically configures its own programming to the detected service or provides a simple means for manual configuration at the installation site.
Further, the performance of power quality tests requires that the type of service and service voltage be known prior to installation so that the meter""s programming can be locked to the appropriate service-dependent thresholds utilized in connection with particularized power quality tests. Therefore, for this additional reason, there remains a need for an electronic meter to automatically detect the service type and voltage to which the meter is installed and which automatically configures its programming to the detected service.
In addition, many new electronic energy meters have begun to take advantage of their programming capabilities by providing limited diagnostic and/or power quality testing. These capabilities are provided by programming stored in read only memory (ROM). Thus, these meters are currently limited in operation to predefined programming, such as predefined sets of tests. Significantly, such meters are also limited to the measurement of only a predetermined set of parameters that have been programmed into such meters, i.e., stored in ROM, during manufacture. Consequently, any change to the measurements or tests supported by the meter must be carried out by replacing the meter""s ROM, i.e., by factory modification. Therefore, there also exists a need for a more flexible electronic energy meter that permits the addition of new measurements or testing capabilities without requiring factory modifications to effect such functionality changes.
The above problems are overcome and the advantages of the invention are achieved in methods and apparatus for metering electrical energy in an electronic meter which automatically detects the service type and voltage to which the meter is installed and which either automatically configures its own programming to the detected service or provides a simple means for manual configuration at the installation site. The electronic energy meter also permits the addition of new measurements or testing capabilities without requiring factory modifications to effect such functionality changes.
The meter includes firmware which measures the characteristics of electrical energy supplied to the meter and which generates characteristic signals reflective of the measured characteristics of the electrical energy. A processor is connected to receive and process the characteristic signals. The processing of the characteristic signals includes selecting and manipulating certain of the characteristic signals and generating characteristic information in response to the selection and generating additional characteristic information in response to the manipulation. It is preferred for the meter to include a memory having reference information stored therein. In such an embodiment, the manipulation of characteristic signals includes retrieving certain of the reference information and generating the characteristic information in response to the selected signals and the reference information.
The present invention is directed to a meter for metering electrical energy provided to the meter via a service type, comprising: means for receiving a measurement request; memory means for storing data in data tables; processor means for performing at least one function responsive to the measurement request and the data in the data tables, and generating output information responsive to the measurement request and the data in the data tables; and output means for outputting the output information in accordance with a predetermined priority scheme.
According to aspects of the present invention, the processor means comprises a first processor and a second processor, and the measurement request is made by one of the first processor and the second processor, and the memory means is an EEPROM
In accordance with an aspect of the present invention, the means for receiving the measurement request is an optical communications external source or an electronic external source.
In accordance with further aspects of the present invention, the measurement request comprises a display measurement request, a power quality measurement request, or an external communications request. Each of the display measurement request, the power quality measurement request, and the external communications request has an associated priority, the priority of the external communications request being greater than the priority of the display measurement request and the priority of the power quality measurement request.
In accordance with a further aspect of the present invention, the means for receiving the measurement request receives the measurement request serially or sequentially.
In accordance with further aspects of the present invention, the data tables comprises a system current test table for testing the system current, a service angle table, a service voltage table, and a phase tolerance table. The system current test table comprises system current thresholds for different service types. The service angle table comprises phase angle information for different service types, and the service voltage table comprises a voltage, at least one tolerance, and a potential indicator threshold for the different service types.
According to further aspects of the invention, the meter further comprises means to determine the service type, and a thresholds table for receiving data corresponding to the service type from the system current test table, the service angle table, and the service voltage table, and further comprises a power quality test table for storing a result of a power quality comparison test performed by the meter. The power quality test table further comprises information referencing a measurement record for the result of the power quality comparison test. The information is a pointer to the measurement record. In an embodiment, the power quality test table further comprises information referencing threshold information in a thresholds table for use in the power quality comparison test.
According to further aspects of the present invention, the meter further comprises a comparison test table for storing comparison tests and a measurement table for storing measurement records. The measurement table comprises information referencing a record in a measurement function table.
In accordance with further aspects of the present invention, the meter further comprises a measurement function table for identifying a digital signal processor (DSP) function to be performed. The measurement function table comprises information referencing a record in a constant table. The record comprises an initialization constant or a calibration constant. The measurement function table further comprises information referencing a record in a conversion table which specifies at least one computation to be performed with the DSP function.
In accordance with further aspects of the present invention, the function comprises display and test selection, display and test parameter adjustment, test definition, or measurement definition. The display and test selection is for inserting predetermined byte sequences into a table to display predetermined measurement quantities and for enabling the meter to perform predetermined power quality tests, each power quality test comprising a predetermined number of steps. The meter further comprises a step counter for counting the predetermined number of steps. An indicator is activated if the step counter exceeds a predetermined threshold.
In accordance with further aspects of the present invention, the test parameter adjustment is for changing the number of line cycle pairs over which an electrical measurement is performed. The test parameter adjustment is for modifying voltage, current, power factor, and time thresholds of the tests that are performed. The test definition is for creating at least one power quality test by combining a plurality of test parameter thresholds. The measurement definition is for creating electrical measurements by combining DSP functions.
In accordance with a further aspect of the present invention, the at least one function is selectable.
Another embodiment within the scope of this invention includes a process for metering electrical energy provided to a meter via a service type, comprising the steps of: receiving a measurement request; storing data in data tables; performing at least one function responsive to the measurement request and the data in the data tables, and generating output information responsive to the measurement request and the data in the data tables; and outputting the output information in accordance with a predetermined priority scheme.